/*
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, either version 3 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

/*
 *    HeadlessEventCollector.java
 *    Copyright (C) 2011-2012 University of Waikato, Hamilton, New Zealand
 *
 */

package weka.gui.beans;

import java.util.EventObject;
import java.util.List;

/**
 * Interface for Knowledge Flow components that (typically) provide
 * an interactive graphical visualization to implement. This allows
 * events that would normally be processed to provide a graphical display
 * to be collected and retrieved when running in headless mode (perhaps on
 * a server for example). A copy of the component that is running with
 * access to a display can be passed the list of events in order to
 * construct its display-dependent output.
 * 
 * @author Mark Hall (mhall{[at]}pentaho{[dot]}com).
 * @version $Revision$
 */
public interface HeadlessEventCollector {

  /**
   * Get the list of events processed in headless mode. May return
   * null or an empty list if not running in headless mode or no
   * events were processed
   * 
   * @return a list of EventObjects or null.
   */
  List<EventObject> retrieveHeadlessEvents();
  
  /**
   * Process a list of events that have been collected earlier. Has
   * no affect if the component is running in headless mode.
   * 
   * @param headless a list of EventObjects to process.
   */
  void processHeadlessEvents(List<EventObject> headless);
}
